Lonex 407x6.03mm High Density Steel Inner Barrel for AEGs

Upgrading the inner barrel is one of the cheapest ways to improve accuracy on an AEG. The Lonex 407mm Enhanced Steel Barrel uses a 6.03mm tight bore to tighten the air seal around standard 0.20–0.25g BBs, which translates to better consistency and a flatter trajectory. Steel construction resists wear and holds its dimensions longer than brass or aluminum alternatives.

Why 6.03mm matters. Most stock barrels run 6.08mm, leaving a small gap between the BB and the bore wall. That gap wastes air pressure and lets the BB wobble. A 6.03mm bore fits tighter around the BB, improving the air seal and making the hop-up more effective. You will notice the difference in grouping, especially at 150 feet and beyond.

Length and fit. At 407mm, this barrel suits carbine-length builds—M4, G36, MP5, and similar platforms with roughly 12–13 inch outer barrels. Measure your existing inner barrel before ordering; a barrel that is too long will bottom out in the gearbox, while one that is too short reduces air volume and can hurt performance. If you are running a short-barrel CQB build, look at 300–360mm options instead.

What this barrel does and does not do. A tight-bore steel barrel improves consistency and can extend effective range, but it will not fix a broken air seal, a worn hop-up unit, or a poorly shimmed gearbox. If your gun shoots soft or groups wide, check the hop-up bucking and nozzle seal first. This barrel is a finishing upgrade, not a cure-all.

Installation is straightforward: remove the gearbox, pull the existing barrel from the hop-up unit, and slide this one in. Use a light coat of silicone oil on the barrel exterior to ease installation and protect the finish. A proper inner barrel upgrade works best with a rotary hop-up chamber and quality bucking—budget parts will bottleneck the improvement.

Includes one inner barrel. Hop-up bucking, nozzle, and chamber are sold separately.